Terrestrial animal welfare has been a matter for exploration for many years. In contrast, approaches towards improving the welfare and humane treatment of aquatic animals are relatively new, as is the thinking behind them. Several issues complicate the process of addressing the welfare of aquatic animals in a consistent manner. These include the following: - the huge diversity among aquatic animals, the majority of which are poikilothermic vertebrates and invertebrates - understanding the practices involved in fisheries, aquaculture and aquatic animal production, and their purpose - the relative paucity of scientific information - understanding the philosophical approaches, policies, guidance and regulations that may influence the provision of optimal welfare and humane practices for aquatic animals. In this paper, the authors attempt to provide an overview of all these elements, relating what is known and understood about these issues for the primary group used in aquaculture and fisheries, finfish, and exploring the factors that may influence the concepts and practices of aquatic animal welfare. These factors seem to be the foundation of all welfare approaches and include: - ethical and moral concepts of animal welfare and humane treatment - whether animals experience suffering from the potentially adverse practices used in their maintenance, management and use - the public and institutional understandings of these issues and their results. These are discussed with the hope that future developments in, and approaches to, aquatic animal welfare will be of use to society, industries and the public.